Black Orchid — Terence Dudley

On a lazy June afternoon in 1925, the TARDIS materializes at the tiny railway station of Cranleigh Halt. Warmly welcomed by the local gentry, the time-travelers look forward to a well-deserved rest from their adventures. After a stunning performance at a friendly cricket match, the Doctor, Tegan, Adric, and Nyssa are invited to a splendid masked ball by Lady Cranleigh and her son, Charles. But a dark menace haunts the secret corridors of Cranleigh Hall. And before the ball is over, the quiet summer will be shattered by the shocking discovery of a brutal murder.